1. Field of the Invention
This invention relates to a main nozzle for an air-jet loom which by suitable tapering of the inner and outer walls of its annular acceleration chamber optimizes the air jet used for inserting the weft into the shed.
2. Discussion of Background
As is well known, in air-jet weaving the weft yarn is inserted into the shed by hydrodynamic coupling between the yarn to be inserted and an air jet, i.e. by transmitting to the weft yarn the entrainment kinetic energy of an air jet generated by a main nozzle.
Various types of main nozzles are already known from the state of the art, all substantially comprising an outer casing provided with a compressed air introduction duct and mixing chamber, and a mixer tube provided with a distributor ring comprising annularly arranged blowing slots and inserted into said outer casing, to form with this latter an annular distribution chamber upstream of said distributor ring and, downstream of said ring, an annular acceleration chamber with conical walls which feeds into said mixing chamber.
It is apparent that with such a construction the cone of the outer wall of said acceleration chamber cannot subtend too large an angle because the annular air jet emerging from said annular blowing slots of said distributor ring would lose too much of its energy in striking against said wall. Neither can said angle be too small otherwise the nozzle will be too long axially, this being a considerable drawback in the case of air-jet looms.